Injection molding factory injection molding product processing common defects and treatment methods
1, water
A. The back pressure is too tight, resulting in sprue overflow, raw materials can not smoothly into the cavity, and because of too much resistance, overheating decomposition;
B. Injection speed is reduced to avoid decomposition of raw materials due to overheating;
C. Adopt multistage injection method, from slow to fast injection molding;
D. Expand the size of the feed gate (gate);
E. The material storage time can not be too long, the material storage speed can not be too fast, to avoid the decomposition of raw materials;
F. The back pressure is too tight or there is material on the screw, resulting in the screw in the storage of material, raw material is difficult to enter the screw, and the storage time is too long, raw material overheating decomposition;
G. Because the raw material flows through the mutated part of the mold, the flow mark (water wire) produced by the raw material can be eliminated by suddenly decreasing the speed here and then increasing the injection speed. The key is that when the material is injected, it is found after this position.
H. The back pressure is too loose, resulting in the material storage, there is air into the screw and the bulk of the water wire, can be adjusted by the storage material back pressure to eliminate this defect;
I. The cold material at the nozzle enters the mold cavity, resulting in water filament on the surface of the product. By adjusting the position of the first injection (low speed injection), the cold material is just controlled in the flow passage, and will not enter the product surface, so as to eliminate the defects on the product surface caused by the cold material entering the mold cavity.
2, shrinkage, shrinkage, shrinkage marks
It is produced by the shrinkage of the plastic volume and is commonly seen in areas of local thickness, such as stiffeners or areas where the foot meets the face.
A. The injection pressure and pressure retaining pressure are insufficient, and the plastic melt filling is insufficient. In general, the injection is carried out in sections, with about 95% filling at high pressure and high speed, and then filling the product at low pressure and low speed, and then pressure retaining.
B. Pressure holding time is insufficient, plastic melt feeding is insufficient, but also easy to cause reflux
C. Injection speed is too slow, plastic melt filling insufficient.
D. The injection volume is insufficient.
E. The material temperature and mold temperature are high, and the cooling is slow. After the cooling and contraction of the plastic is complete, the shrinkage and subsidence will occur.
F. The size of runner and gate is small, the pressure loss increases, and the gate solidifies too early, and the feeding is not good.
G. Part of the meat is too thick.
H. If the CUSHIONVOLUME of the injection molding machine is insufficient or the check valve does not operate smoothly, the uneven wall thickness of the product will also shrink and there will be a wave phenomenon on the surface of the product.
3, burning
A. Trapped air area (shell) to strengthen the exhaust, so that the air timely discharge.
B. Reduce the injection pressure, but it should be noted that the injection speed slows down after the pressure drops, which is easy to cause the deterioration of flow marks and weld marks.
4, flying edge, rough edge, batch front
A. High pressure and high speed injection, leading to elastic deformation of the mold, the parting surface produces gaps and the product produces flanges, using two injection, first high pressure and high speed injection, then low pressure and low speed injection,
In order to achieve the purpose of elastic retraction of the mold at low pressure and eliminate the flying edge;
B. When THE clamping force is insufficient, the high pressure plastic injected into the cavity causes the gap between the parting surface or the fitting surface of the insert, and the plastic melt overflows into this gap.
C. The foreign body attached to the parting surface leads to a gap in the closing mold.
D. Try not to get the gate too close to the insert/insert.
5. Cold material lines
A. The injection pressure of a section is too small, resulting in a section of injection, the cold material is not controlled in the flow passage, and it flows into the surface of the product in the secondary injection;
B. A period of speed is too slow or too fast, will also lead to the occurrence of the above phenomenon;
C. The injection end position of the first section is too large, which leads to the injection of the second section before the cold material is finished, which leads to the cold material entering the model cavity under high pressure and high speed (on the contrary, if the position is too small, water ripples will be generated at the gate edge);
D. Die temperature or nozzle temperature is too low, resulting in cold material;
E. Cold material hole (flow passage) is too small; The design doesn't make sense.
6, melting seams
A. Reduce the number of sprue.
B. Add a material overflow well near the fusion part, move the fusion line to the overflow well, and then cut it off.
C. Adjust the gate position (uneven wall thickness).
D. Change the position and number of the gate, and move the position of the fusion line to another place.
To improve the
A. Strengthen the exhaust in the fusion line area, quickly evacuate the air and volatiles in this part.
B. Increase the material temperature and mold temperature, enhance the fluidity of plastic, improve the material temperature during fusion.
C. Increase the injection pressure and increase the size of pouring system appropriately.
D. Increase the ejection speed at the weld line.
E. Shorten the distance between the gate and the weld area.
H. Reduce the use of release agents.
